I solved the problem removing the mouse . Disassemble the mouse (2 screws under the slide sticker on the back, a slide under the front sticker and a sticker under the guarantee) and open carefully (2 small clips) button on which the problem appears, then just scratch the very small block with something gold. Be careful because the copper piece that makes contact is in an unstable position and it is not so easy to put back into the correct position.

I solved the problem removing the mouse . Disassemble the mouse (2 screws under the slide sticker on the back, a slide under the front sticker and a sticker under the guarantee) and open carefully (2 small clips) button on which the problem appears, then just scratch the very small block with something gold. Be careful because the copper piece that makes contact is in an unstable position and it is not so easy to put back into the correct position.